bcm2708: fix gpio_to_irq() name clash

<mach/gpio.h> has gpio_to_irq() defined as a macro. the macro is
obviously intended as the direct implementation of that
functionality. unfortunately the gpio subsystem offers a public
function of the same name through <linux/gpio.h>. one has to be very
careful to include <mach/gpio.h> before <linux/gpio.h> - otherwise the
code will compile but only work by chance. board code will certainly
not work - the gpio driver is simply not loaded at that time.

fix the clash by renaming the offending macros from <mach/gpio.h>,
together with their uses.
gpio: support low and high level interrupts
Merge branch 'rpi-3.11.y' of git://github.com/raspberrypi/linux into dave-3.11.y
Revert "bcm2708: fix gpio_to_irq() name clash"

This reverts commit e59870081d5f6af31e77078dec77a8343daddb47.

Conflicts:
	arch/arm/mach-bcm2708/bcm2708_gpio.c
Merge pull request #506 from jfasch/rpi-3.11.y-fix-gpio_to_irq

Please pull: NEED_MACH_GPIO_H vs. gpio_to_irq() woes
Merge branch 'rpi-3.11.y' of git://github.com/raspberrypi/linux into dave-3.11.y